Measurement experience with a single-phase short circuit in an electrical network of 0.4 kV

Abstact. The work is aimed at instrumental measurement of the parameters of the 0,4 kV electrical network when a single-phase short circuit of the phase wire to ground and the phase wire to zero occurs in it. The measurement has been carried out using the MZC-300 device. The results obtained empirically have been compared with the calculated values obtained by the method of calculating short-circuit currents in accordance with GOST 28249-93 and by the simplified «phase-zero» loop method. The actual value of the metal single-phase short circuit current obtained by measurement using the MZC-300 device is 230 A, which is 14%-36% more than the calculated values obtained using methods according to GOST 28249-93 and the simplified «phase-zero» loop method. The value of the single-phase short-circuit current when the phase wire breaks and it falls to the ground is 2,52 A, which is 91 times less than the metal short-circuit current between the phase and zero conductor at the same point of the 0.4 kV electrical network. Currently known technical means and methods of protection of rural 0,4 kV electrical networks in the air version do not allow to effectively eliminate single-phase short circuit modes when a phase wire falls to the ground.